Client station configured for operation based on persistent resource allocation information

ABSTRACT

Methods and apparatus for communicating and utilizing persistent allocation of resources are described herein. A base station may allocate persistent resources to a client station, and may associate the client station or persistent resource allocation with a particular shared NACK channel. The base station may monitor the NACK channel for a NACK indicating a map error. The base station may monitor the resource allocation to implicitly determine a map error. The base station may resend one or more persistent resource allocation information elements in response to the NACK or implicit error determination. A client station having a persistent resource allocation may monitor persistent resource allocation information elements in map messages and/or may indicate failure to receive a persistent resource allocation information element in a NACK message on a shared NACK channel.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/879,632, filed Oct. 9, 2015, which is a continuation of U.S. patentapplication Ser. No. 14/271,596, filed May 7, 2014, which issued as U.S.Pat. No. 9,161,341 on Oct. 13, 2015, which is a continuation of U.S.patent application Ser. No. 13/861,013, filed Apr. 11, 2013, whichissued as U.S. Pat. No. 8,732,541 on May 20, 2014, which is acontinuation of U.S. patent application Ser. No. 12/204,719, filed Sep.4, 2008, which issued as U.S. Pat. No. 8,423,853 on Apr. 16, 2013, whichclaims the benefit of U.S. Provisional Application No. 61/013,622 filedDec. 13, 2007 and U.S. Provisional Application No. 60/971,526, filedSep. 11, 2007. The above-referenced applications are incorporated byreference as if fully set forth.

FIELD OF INVENTION

The invention relates to the field of wireless communications. Moreparticularly, the invention relates to the field of resource allocationin a wireless communication system.

BACKGROUND

Wireless communication systems may support discontinuous transmission inwhich the various parties to a communication link use resources only asneeded. Limiting the allocation and consumption of resources to thosedevices actively engaged in communications increases the efficiency of awireless communication system. However, each device may need to requestan allocation of resources before it is granted the opportunity tocommunicate. The request and grant of communication resources can itselfconsume a large amount of resources that otherwise could be used tosupport additional users or provide increased bandwidth to active users.

It is desirable to minimize the amount of resources consumed inrequesting and granting resources for discontinuous communications.However, there remains the need to maximize the flexibility ingenerating access requests and allocating the resources associated withthe access requests.

SUMMARY

Methods and apparatus for communicating, monitoring, controlling andutilizing persistent allocation of downlink and uplink resources aredescribed herein. In one aspect, a method of persistent resourceallocation is disclosed in which a base station schedules a candidateclient station for a persistent resource allocation, associates thecandidate client station with a shared NACK channel, configures apersistent allocation information element indicating the persistentresource allocation and transmits the persistent allocation informationelement. The base station may further configure the persistentallocation information element to indicate a pseudo random code whichdefines the shared NACK channel. It may also receive a NACK message overthe shared NACK channel and transmit an indication of a set of recentchanges made to persistent allocations corresponding to a set of clientstations associated with the shared NACK channel. In addition, it mayreceive a NACK message over the shared NACK channel, determine that nochanges have been made to persistent allocation corresponding to a setof client stations associated with the shared NACK channel and transmita no-changes-made indication to the set of client stations. The basestation may detect little or no energy from the candidate client stationon the persistent resource allocation and retransmit the persistentallocation information element. The persistent resource allocation maybe configured to carry an HARQ packet stream and the base station maydetect a series of failed HARQ packet transfers and retransmit thepersistent allocation information element.

In another aspect, a method of persistent uplink resource allocation isdisclosed in which an element of the communication network communicatesa persistent resource allocation information element, receives a NACK ona predetermine shared NACK channel and retransmits at least a portion ofthe persistent resource allocation information element to a group ofclient stations associated with the shared NACK channel.

A method of persistent uplink resource allocation is also disclosed inwhich a resource map is received. An attempt is made to decode apersistent allocation information element within the resource map. A mapNACK is selectively transmitted over a shared map NACK channel if thepersistent allocation information element fails to successfully decode.In one aspect, transmission of data is ceased on an uplink channelassociated with a most recently received downlink persistent allocation.According to one aspect, a map NACK channel recovery process begins inresponse to a failure to receive an expected response to transmission ofthe map NACK. According to another aspect, a second persistentallocation information element is received that indicates that a NACKmessage was received and no changes were made.

Also described is a base station which executes a method of recoveringfrom an error condition in a system using a shared NACK channel. Thebase station sends an uplink persistent allocation information elementspecifying a first persistent allocation for a client station. If thebase station detects little or no signal energy from the client stationon the first persistent allocation, the base station resends the uplinkpersistent allocation information element to the client station.

Alternatively, the base station may recover from an error condition bysending an persistent allocation information element specifying a firstallocation to a client station for a purpose of carrying HARQ traffic,by detecting a series of failed HARQ packet transfers associated withthe first allocation, and resending the persistent allocationinformation element to the client station.

Also described is a client station which executes a method of recoveringfrom an error condition in a system using a shared map NACK channel byreceiving a persistent allocation information element from a basestation for a purpose of carrying HARQ traffic over a first allocation,detecting a series of failed HARQ packet transfers associated with thefirst allocation and by sending a map NACK channel error message to thebase station.

A base station may establish a global map NACK channel for persistentallocation assignments, send an uplink persistent allocation informationelement to a client station indicating an associated shared NACKchannel, receive a global NACK message on the global map NACK channeland resend a set of recently changed persistent allocation informationelements to a set client stations associated with two or more sharedNACK channels.

In one aspect, a client station fails to receive a persistent allocationinformation element while no persistent allocation is currently assignedto the client station. The client station determines that no shared mapNACK channel assignment is active and sends a global map NACK message onthe global map NACK channel.

Further described is a base station having a group scheduler configuredto schedule a candidate client station for persistent uplink resourceallocation, a persistent DL/UL IE generator configured to associate thecandidate client station with a shared map NACK channel and to configurea persistent allocation information element identifying a persistentresource allocation and a transmitter configured to transmit thepersistent allocation information element. The base station may beconfigured to receive a map NACK message over the shared map NACKchannel and the persistent DL/UL IE generator is further configured todetermine a set of recent changes made to persistent allocationscorresponding to a set of client stations associated with the sharedNACK channel for retransmission.

In yet another aspect, the client station has a receiver configured toreceive a resource map, a DL/UL-map module configured to determinewhether a persistent allocation information element is within theresource map and to attempt to decode the persistent allocationinformation element, and a NACK module configured to selectively createa map NACK message for transmission over a shared map NACK channel ifthe DL/UL module is unable to successfully decode the persistentallocation information element.

Certain additional means for implementing all of these aspects are alsodisclosed. Many aspects may be stored in a computer-readable medium.Additional aspects of the invention are detailed in the descriptionprovided herein and associated figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, objects, and advantages of embodiments of the disclosurewill become more apparent from the detailed description set forth belowwhen taken in conjunction with the drawings, in which like elements bearlike reference numerals.

FIG. 1 is a simplified functional block diagram of an embodiment of awireless communication system.

FIG. 2 is a simplified functional block diagram of an embodiment of abase station implementing persistent downlink or uplink resourceallocation.

FIG. 3 is a simplified functional block diagram of an embodiment of aclient station configured to operate using persistent downlink or uplinkresource allocation.

FIG. 4 is a simplified timing diagram of an embodiment of a persistentresource allocation.

FIG. 5 is a simplified timing diagram of an embodiment of map NACKmessaging in a system having persistent resource allocation.

FIG. 6 is a simplified flowchart of an embodiment of a method ofpersistent downlink or uplink resource allocation.

FIG. 7 is a simplified flowchart of an embodiment of a method ofresource reallocation in the presence of error correction.

FIG. 8 is a simplified flowchart of an embodiment of a method of errorcorrection signaling in a client station.

FIG. 9 is a flowchart of an embodiment of a method of addressing apersistent allocation map error from the perspective of a base station.

FIG. 10 is a flowchart of an embodiment of a method of addressing adownlink persistent allocation map error from the perspective of aclient station.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Methods and apparatus for communicating and utilizing persistentallocation of downlink or uplink resources are described herein. In thisdescription, the communication path from the base station to the clientstation is referred to as a downlink (DL) and the communication pathfrom the client station to the base station is referred to as an uplink(UL).

When the base station assigns a standard non-persistent downlink oruplink allocation for use by a client station, the allocation is validfor a predetermined frame, such as a frame in which the allocation isgranted or the frame following the frame in which the allocation isgranted, depending on the allocation relevancy. In contrast, when a basestation assigns a persistent downlink or uplink allocation to a clientstation, the allocation typically remains valid for multiple futuredownlink or uplink frames. Thus, the client station does not need torepeat a request for uplink resources periodically over a long series offrames. Nor does the base station need to expressly and repeatedlyidentify a downlink or uplink resource allocation in a series ofdownlink or uplink map information element (IE) messages when the basestation implements persistent resource allocation.

In some systems, a client station requests a persistent downlink oruplink allocation when the client station is producing a data streamwhich is predictably periodic and in which the packets are generallyfixed in size. For example, when a client station has established avoice over Internet protocol (VOIP) connection, a steady stream of voicepackets will typically be produced. The base station can verify that thedownlink or uplink resource request meets the criteria for persistentresource allocation and allocate persistent downlink or uplink resourcesas part of a persistent downlink or uplink map information element (IE)message that is transmitted to the client stations in the system.

In a typical system, the base station has the ability to determine thata client station is a candidate for a persistent downlink or uplinkresource allocation. For example, the base station can determine that aclient station is a candidate for a persistent downlink or uplinkresource allocation based on one or more parameters. The parameters caninclude, for example, repeated requests for uplink resource allocationsfrom the client station, the consistency of the resource allocationrequested, stability of characteristics of a wireless channel betweenthe base station and the client station, knowledge of the packet arrivaldistribution, and the type of connection. As an example, if theconnection is in support of VOIP communication, the base stationtypically knows that the packet arrival pattern is a good candidate forpersistent resource allocation.

The persistent allocation remains dedicated to the client station infuture frames until a predetermined terminating event, such as a passageof time, passage of a predetermined number of frames, the base stationnotifying the client station that the resource has been deallocated, abase station reallocating all or part of resources allocated to anotherclient station, and the like or some combination thereof. The basestation may deallocate a persistent resource by sending a revisedpersistent downlink or uplink map IE which no longer allocates apersistent resource to the client station or reallocates resources tothe client station. In one aspect, the base station sends an expressdeallocation message.

The base station can group the client station resource request andresource allocation to any one of multiple persistence groups. The basestation can select a persistence group for a particular client stationbased on such factors as a traffic arrival pattern, a power class of theclient station, load balancing at the base station, and the like or somecombination thereof.

The base station can allocate uplink resources to the client stations ineach of the persistence groups such that members of each persistencegroup transmit in a frame distinct from any other persistence group.Similarly, the base station can allocate persistent resources to theclient stations in each of the persistent groups such that members ofeach persistence group transmit in a frame distinct from any otherpersistence group. If the base station allocates both persistentdownlink and uplink resources to a particular client station, thepersistence groups will coincide. For example, each persistence groupcan be associated with a group cycle number and a persistent resourceallocation can be valid for uplink frames associated with the groupcycle index. In one embodiment, the persistence groups can be timecycled in a round-robin schedule in order to provide uniform access anda uniform rate across the multiple persistence groups. A simpleimplementation utilizes the frame number and group cycle index toidentify the active persistence group associated with a particularframe. The active persistence group can be identified by determining themodulo function of the frame number and the total number of persistencegroups, typically notated as MOD (frame number, N), and comparing theresult against the group cycle index, where N represents the number ofpersistence groups. (The modulo operation returns the remainder ofdivision of one number by another. Given two numbers, a (the dividend)and x (the divisor), mod (a,x) is the remainder, of division of a by x.For instance, the expression MOD (7,3) would evaluate to 1, while MOD(9,3) would evaluate to 0.)

The client station need not have any knowledge of its group cycle indexand only needs to know the number of persistence groups, N. The clientstation can determine its group cycle index by determining the value ofMOD (frame number, N) for the first frame number for which it isallocated persistent downlink or uplink resources. Groups may also beidentified and associated with client stations explicitly bycommunicating a period parameter in the persistent allocation IE. In oneaspect, an express indication of the period of the persistent allocationis sent in the UL-MAP information element, thus eliminating the need forthe use of a modulo function.

In a typical OFDMA system, the base station can distinguish data comingfrom the various client stations according to time (number of symbols)and frequency (number of subcarriers). Of course in other systems, thebase station may distinguish data coming from the various clientstations according to some other physical layer (PHY) characteristicsassociated with the system.

To reduce overhead, the base station typically does not assignindividual physical layer units to the client stations. Instead, thephysical layer units are grouped together into “allocation units.” Thebase station assigns resources to the client stations by specifyingallocation units, rather than designating individual physical layerunits. An allocation unit can be, for example, a combination of apredetermined number of subcarriers and symbols. In one embodiment, aminimum allocation unit is referred to as a “slot,” and a slotencompasses a predetermined number of subcarriers in one or more OFDMAsymbols.

According to IEEE 802.16, communication on both the uplink in thedownlink are divided into frames of fixed a length. Each frame includesa downlink subframe and uplink subframe. The downlink subframe typicallyincludes link management transmissions (such as synchronization signalsand the like), overhead channels, a number of downlink allocation unitsfor carrying user data from the base station to the client stations aswell as other types of overhead and data transmissions. The uplinksubframe includes many of these same categories of transmissions,including uplink allocation units for carrying user data from the clientstation to the base station and control signaling channels for systemcontrol, administration and the like.

Modulation is the process of encoding information onto a signal fortransmission. Many modulation schemes are well known in the artincluding binary phased shift keying (BPSK), quadrature phase shiftkeying (QPSK) and quadrature amplitude modulation (QAM.) Modulationschemes differ from one another according to the amount of data carriedby any one symbol. Higher order modulation schemes carry more data persymbol. For example, a 16 QAM symbol carries 4 bits of data per symbolwhile BPSK modulation carries only one bit of data per symbol.

Higher order modulation schemes are more susceptible to channelconditions than lower order modulation schemes. Thus, use of a higherorder modulation scheme is more likely to result in errors than use of alower order modulation scheme under poor channel conditions.

However higher order modulation schemes are more efficient in terms ofthe amount of information that can be transferred over the wireless linkin a fixed period of time. Thus, within a fixed period of time, moredata can be transferred over the link using a higher order modulationscheme than a lower order modulation scheme if channel conditions aregood. Thus, transmissions using lower order modulation schemes are morerobust, but less efficient, and transmissions using higher ordermodulation schemes are less robust but more efficient.

In order to improve the performance of the wireless link, errorcorrection coding, such as forward error correction (FEC), can beapplied at the transmitter. Using complex error correction schemes, sometype of redundancy is introduced in the data before transmission. Thecode rate typically refers to the length of the uncoded informationdivided by the length of the resulting encoded information. Theredundancy can be used to correct for errors which are introduced by thewireless channel. The effectiveness of a coding scheme is measured interms of coding gain, which can be expressed as the difference betweenthe signal to noise level required to reach the same bit error ratelevel for encoded and uncoded data. Modern error correction codingtechniques provide substantial coding gains. However, due to theredundancy introduced, the use of error correction coding typicallydecreases the effective rate at which data is transmitted over thechannel. Therefore, transmissions using codes having higher redundancyrates are more robust, but less efficient than transmissions using codeshaving lower redundancy rates.

The IEEE 802.16e standard and its progeny define a variety of modulationand coding scheme (MCS) combinations. The MCS specifies a type ofmodulation as well as a type of forward error correction which theclient station is to use on the uplink transmission. The MCScombinations accommodate the large variation in performance associatedwith the client stations scattered throughout the coverage area. Properselection of an MCS combination is important to both the efficiency andperformance of a wireless link.

When the base station assigns an allocation unit to a specific clientstation, it also specifies the MCS combination to be used on theallocation. This may be typical for both persistent and nonpersistentresource allocations.

Once the base station sends a persistent resource allocation, generallyit need not resend the resource allocation unless a change to thedownlink or uplink resource allocations makes it advantageous to resendthe resource allocation. For example, a new full or partial persistentuplink map IE may be sent when there is a need to change the size of theallocation. Such a size change may occur if the operating conditions ofthe client station assigned a persistent allocation are altered orotherwise change to such a degree that a new MCS combination isadvantageous. Therefore the base station typically resends thepersistent downlink or uplink map IE to identify the new MCS combinationand assign the client station fewer or more allocation units asappropriate. In addition, a new persistent downlink or uplink map IE maybe sent when a voice activity state changes, thus changing the rate ofoccurrence of the persistent allocation. In addition the base stationtypically resends the persistent uplink map IE if requested by theclient station to do so, and may alter a persistent downlink mapaccordingly. Of course, the base station can be configured toperiodically resend the persistent downlink or uplink map IE even if nochanges have occurred to permit client stations in the base stationcoverage area to verify the persistent downlink and uplink resourceallocations. In addition, there may be several other instances in whichpersistent downlink and uplink map IE are resent, some of which arediscussed below.

The descriptions contained herein generally focus on OrthogonalFrequency Division Multiple Access (OFDMA) wireless communicationsystems, and particularly are directed towards IEEE 802.16 wirelesscommunication systems or wireless communication systems based on IEEE802.16e as modified or otherwise extended by the methods and apparatusdescribed herein. However, the implementation of persistent downlink oruplink resource allocation scheme in an IEEE 802.16e system is usedmerely as an example. The use of persistent downlink or uplink resourceallocation scheme can be implemented in virtually any type of wired orwireless communication system.

FIG. 1 is a simplified functional block diagram of an embodiment of awireless communication system 100. The wireless communication system 100includes a plurality of base stations 110 a, 110 b, each supporting acorresponding service or coverage area 112 a, 112 b. Each base station110 a and 110 b can be coupled to one another and a supporting network(not shown) via a combination of a wired and wireless links. The basestation, for example 110 a, can communicate with wireless devices withinits coverage area 112 a. For example, the first base station 110 a canwirelessly communicate with a first client station 130 a and a secondclient station 130 b within the coverage area 112 a over a downlink 116a and an uplink 116 b.

Although for simplicity only two base stations are shown in FIG. 1, atypical wireless communication system 100 includes a much larger numberof base stations. The base stations 110 a and 110 b can be configured ascellular base station transceiver subsystems, gateways, access points,radio frequency (RF) repeaters, frame repeaters, nodes or any wirelessnetwork entry point.

In a typical system, the base stations 110 a and 110 b also communicatewith each other and a network control module (not shown) over backhaullinks (also not shown.) The backhaul links may include wired andwireless communication links. The network control module providesnetwork administration and coordination as well as other overhead,coupling and supervisory functions for the wireless communicationsystem. The network control module also couples the wireless link systemto other communications systems such as the Internet, conventiontelephone systems and the like.

Although only two client stations 130 a and 130 b are shown in thewireless communication system 100, typical systems are configured tosupport a large number of client stations. The client stations 130 a and130 b can be mobile, nomadic or stationary units. The client stations130 a and 130 b are often referred to as, for example, mobile stations,mobile units, subscriber stations, wireless terminals or the like. Aclient station can be, for example, a wireless handheld device, avehicle mounted device, a portable device, client premise equipment, afixed location device, a wireless plug-in accessory or the like. In somecases, a client station can take the form of a handheld computer,notebook computer, wireless telephone, personal digital assistant,wireless email device, personal media player, meter reading equipment orthe like in may include a display mechanism, microphone, speaker andmemory.

In one example, the wireless communication system 100 is configured forOrthogonal Frequency Division Multiple Access (OFDMA) communications.For example, the wireless communication system 100 can be configured tosubstantially comply with a standard system specification, such as IEEE802.16e or some other wireless standard. The wireless communicationsystem 100 can support the persistent downlink or uplink resourceallocation described herein as an extension to the system standard or aspart of a system standard.

The wireless communication system 100 is not limited to an OFDMA system,and use of persistent downlink or uplink resource allocation describedherein is not limited to application in OFDMA systems. The descriptionis offered for the purposes of providing a particular example of theoperation of persistent downlink or uplink resource allocation in awireless communication environment.

Each base station, for example 110 a, can supervise and control thecommunications within its respective coverage area 112 a. Each activeclient station, for example 130 a, registers with the base station 110 aupon entry into the coverage area 112 a. The client station 130 a cannotify the base station 110 a of its presence upon entry into thecoverage area 112 a, and the base station 110 a can interrogate theclient station 130 a to determine the capabilities of the client station130 a.

The base station 110 a assigns one or more temporary identifiers to eachdata stream coming from a particular client station 130 a for use inidentifying the a data stream to the base station 110 a. The temporaryidentifier can be referred to as a Connection Identifier (CID). Thesystem can allocate a predetermined range of numbers or characters forthe CID, and reserves a number of bits necessary to support the maximumCID value in each message requiring a CID value. More than one CID maybe associated with a particular client station. For example, if a clientstation is conducting a voice over Internet protocol (VoIP) call whilealso downloading information from the Internet, the VoIP data streamwill be assigned one CID and the Internet data stream will be assignedanother CID. A base station allocates resources for a particular CID,rather than for particular client station. In one embodiment, the basestation may allocate a persistent resource for one data connectionassociated with a client station while continuing to sporadically assignnon-persistent allocations to another data connection associated withthe same client station on an as needed basis. Thus, although forsimplicity's sake a persistent allocation is typically referred toherein as assigned to a particular client station, and many systems, thepersistent allocations are assigned per connection rather than perclient station.

The client stations 130 a and 130 b communicate information to the basestation 110 a on the uplink. For example the client stations reportinformation related to current operating conditions as well as requestuplink resources. According to IEEE 802.16, each base station, forexample 110 a, can allocate some resources to support one of more randomaccess channel (RAC), dedicated control channel, media access controllayer (MAC) signing, channel quality indication channel (CQICH), out ofband signaling, piggy back messaging or other control signaling pathused by the client stations 130 a and 130 b for such uplinkcommunications. According to IEEE 802.16, one such a dedicated channelfor transmission of allocation requests is referred to as a fastfeedback channel.

The base station 110 a can periodically allocate resources to supportthe control signaling channel. In one embodiment, the base station 110 acan support one or more random access channels, dedicated channels etc.in each uplink frame. For example, a base station 110 a can allocate aportion of the uplink resources to one or more random access and/ordedicated channels. The base station 110 a can allocate, for example, atime, duration, and number of OFDM subcarriers on the uplink portion forthe random access and/or dedicated channels. Each of the random accessand/or dedicated channel parameters may be static or may be dynamic.

The client station 130 a may transmit a bandwidth request to the basestation 110 a using the random access channel, dedicated controlsignaling channel or other channel. In response to the request, the basestation 110 a may allocate uplink resources to the client station 130 a.

The wireless communication system 100 can reduce the need for acontinual request and allocation of resources by utilizing persistentuplink resource allocations. A client station, e.g. 130 a may request apersistent resource allocation or a base station, e.g. 110 a maydetermine that a client station 130 a is a candidate for a persistentuplink resource allocation. Similarly, a base station 110 a maydetermine that a particular client station 130 a is a good candidate forpersistent downlink resource allocation, and may allocate persistentdownlink resources to eliminate the overhead and resources needed tocontinually communicate downlink resource allocations to the clientstation.

Each of the base station 110 a and client station 130 a can implementone or more processes for detecting and/or communicating an error in thereceipt or processing of persistent resource allocation assignments. Forexample, each client station 130 a can affirmatively acknowledge (ACK)receipt of a persistent downlink or uplink resource allocation IEmessage. Conversely, each client station 130 a can communicate anegative acknowledgement (NACK) upon determining a failure to receive apersistent downlink or uplink resource allocation IE message orotherwise determining an inability to decode the persistent downlink oruplink resource allocation IE message sent by a serving base station,e.g. 110 a.

The base station 110 a can determine the presence of the errorcondition, either through failure to receive an affirmativeacknowledgement, through receipt of a negative acknowledgement, or viasome other process. The base station 110 a can retransmit the persistentdownlink or uplink resource allocation IE message in response todetermining the error condition. In one embodiment, the base station 110a can retransmit the entire persistent downlink or uplink resourceallocation IE message. In another embodiment, the base station 110 a canretransmit a portion of the persistent downlink or uplink resourceallocation IE message that relates to the client station 130 acommunicating the error condition.

FIG. 2 is a simplified functional block diagram of an embodiment of abase station 200 implementing persistent downlink and uplink resourceallocation and resource allocation retransmission for error correction.The base station 200 can be, for example, one of the base stations inthe wireless communication system of FIG. 1.

The base station 200 includes an antenna 202 that can be coupled to areceiver 210 and transmitter 280 within the base station 200. AlthoughFIG. 2 illustrates a single antenna 202, the antenna 202 can be one ormore antennas configured to support multiple transmit and receiveoperating bands, multiple input multiple output (MIMO) operation, beamsteering, special diversity and the like. If the base station 200supports frequency division multiplexing of the transmit and receivebands, the base station 200 can include a duplexor (not shown) toisolate the transmit signals from the receiver 210. The receiver 210 andtransmitter 280 can be distinct or can be part of a transceiver.

The receiver 210 is configured to receive the uplink transmissionstransmit by a client station (not shown), such as one of the clientstations of FIG. 1. Initially, a client station can synchronize andregister with a base station 200 once the client station enters acoverage area of the base station 200 or upon waking up from a sleep oridle state.

The receiver 210 can receive a request for uplink resources in a requestfrom a subscriber transmitted over a random access channel, fastfeedback channel, piggyback data channel, MAC signaling, CQICHsignaling, in band or out of band messaging, dedicated control channelor any other type of control signaling channel. A control signalingchannel processor 220 is coupled to the receiver 210 and operates todetermine the presence of an uplink allocation request. The controlsignaling channel processor 220 may also perform associated duties incombination with one or more functional modules to identify therequesting client station and to identify the nature and size of theresource allocation request. For example, the control signaling channelprocessor 220 may operate in conjunction with a downlink signalprocessor 270 to communicate additional information to the clientstation that enables the client station to communicate the additionalbandwidth, nature, and identity information.

A persistent candidate processor 230 can process the downlink and uplinkresource allocation request, for example, processed by the controlsignaling channel processor 220 to determine whether the requestingclient station is a good candidate for persistent resource allocation.The persistent candidate processor 230 can also determine if a clientstation is a good candidate for persistent downlink resource allocation.The persistent candidate processor 230 can, for example, determine anexpress request for a persistent channel or may monitor one or moreparameters to determine whether the client station is a candidate forpersistent resource allocation in the downlink, uplink, or both. In oneaspect, the express request for persistent channel is made by anotherelement of the base station or infrastructure.

The persistent candidate processor 230 may also monitor the receivedsignal to determine a channel characteristic associated with therequesting client station. Alternatively, the persistent candidateprocessor 230 may monitor the received signal for feedback informationfrom the client station characterizing its channel characteristics. Suchsignaling may be processed by the control signaling channel processor220.

The persistent candidate processor 230 can be coupled to a groupscheduler 240 and to a downlink/uplink map generator 260. If thepersistent candidate processor 230 determines that the resource requestand client station are not candidates for persistent allocation, thepersistent candidate processor 230 can signal the DL/UL map generator260 to generate a non-persistent downlink or uplink resource allocation.

If the persistent candidate processor 230 determines that the resourcerequest and client station are good candidates for persistentallocation, the persistent candidate processor 230 can communicate theinformation to the group scheduler 240. The group scheduler 240 can beconfigured to schedule the persistent allocation to one or more groupfrom a predetermined number of groups. The group scheduler 240 candetermine the group or groups based on a variety of parameters andmetrics. For example, the group scheduler 240 can attempt to balancepersistent allocations across each of the groups or may operate tooptimize some other constraint or metric.

The group scheduler 240 can communicate the group information to apersistent DL/UL map IE generator 250 that operates to generate thepersistent DL/UL allocation IE for the group, including the persistentresource allocation for the requesting client station.

The persistent DL/UL IE generator 250 can communicate the persistentDL/UL allocation IE to the DL/UL map generator 260 for inclusion in therespective DL-MAP or UL-MAP. The DL/UL map generator 260 can beconfigured to generate the DL-MAP and UL-MAP including any persistentand non-persistent resource allocations.

The DL/UL map generator 260 couples the UL-MAP information element tothe downlink signal processor 270 which creates the final message fortransmission over the downlink. The downlink information can be coupledto the transmitter 280 for transmission in the coverage area supportedby the base station 200.

The base station 200 can determine and communicate persistent resourceallocations periodically, in response to an updating event or trigger,or some combination thereof. In one embodiment, the base station 200 canbe configured to update and transmit persistent resource allocation IEseach frame, where a frame corresponds to a predetermined number ofsymbols, packets, or some other measure of information.

The base station 200 can also include a NACK/ACK processing module 290coupled to the receiver 210 output. The NACK/ACK processing module 290can be configured to determine, for example, the presence of apersistent resource allocation map error condition. (A map error occurswhen a client station fails to properly receive the persistent downlinkor uplink map IE in a frame which may have included a change to itscurrent persistent allocation configuration, for example, such as, aninitial grant of a new persistent allocation, a change to a currentlyactive persistent allocation or termination or suspension of a currentlyactive persistent allocation.) The NACK/ACK processing module 290 can beconfigured to determine the error condition expressly or implicitly. TheNACK/ACK processing module 290 can determine the error conditionexpressly by monitoring the received signals for ACK and/or NACKmessages communicated by the client stations. The NACK/ACK processingmodule 290 can determine the error condition implicitly by monitoringthe received signals and monitoring for the absence of received signalsover persistent resource allocations.

The NACK/ACK processing module 290 can communicate the presence of anerror condition to the DL/UL map generator 260 and the persistent DL/ULIE generator 250. The NACK/ACK processing module 290 can also determinethe identity of a client station or group of client stations associatedwith the error condition. The NACK/ACK processing module 290 cancommunicate the identity information to the DL/UL map generator 260 andthe persistent DL/UL IE generator 250.

The persistent DL/UL IE generator 250 can generate a persistent DL or ULallocation IE that repeats at least a portion of a previouslytransmitted persistent allocation IE. The repeated portion of thepersistent allocation IE can correspond to the identified client stationor group of client stations associated with the error condition. TheDL/UL map generator 260 generates the error correction DL-MAP or UL-MAP,as needed, and retransmits at least the portion of a previouslytransmitted persistent resource allocation IE. In the absence of maperror grouping, where the base station is unable to determine whichclient station or group of client stations transmitted the NACK, thebase station may retransmit the entire persistent allocation IE.

FIG. 3 is a simplified functional block diagram of an embodiment of aclient station 300 configured to operate using persistent downlink anduplink resource allocation. The client station 300 can be, for example,one of the client stations illustrated in the wireless system of FIG. 1.

The client station 300 can include an antenna 302 coupled to a receiver310 and a transmitter 370. Although a single antenna 302 is shown asshared between a transmitter 370 and receiver 310, multiple antennas canbe used.

The receiver 310 can be configured to operate to receive the downlinktransmissions from a base station such as the base station of FIG. 2. ADL/UL map module 320 coupled to the receiver 310 can be configured toextract the DL-MAP information element and the UL-MAP informationelement from the downlink signal.

The DL/UL map module 320 can be configured to examine the DL-MAP todetermine if the client station 300 has been allocated persistent ornon-persistent downlink resources and can examine the UL-MAP todetermine whether the client station 300 has been granted uplinkresources, and if so, whether the allocation is persistent ornon-persistent.

If the DL/UL map module 320 determines that the DL-MAP informationelement or UL-MAP information element indicates a persistent resourceallocation for the client station, the DL/UL-map module 320 can storethe persistent DL or UL map IE in a storage device 324. The DL/UL-mapmodule 320 can also communicate a persistent allocation to a group cycleindex module 340 that is configured to determine the group cycle indexassociated with the persistent resource allocation. The group cycleindex module 340 can communicate the group cycle index value to asynchronizer 360 to permit the synchronizer 360 to synchronize the ULtransmissions to the proper frames. The synchronizer 360 can communicatethe group cycle index value to the receiver 310 to synchronize thereceiver 310 to the proper downlink frames.

The DL/UL-map module 320 can also communicate the persistent UL-MAP andDL-MAP information to a resource mapper 330. The resource mapper 330 canbe configured to compare the current persistent allocation map againstthe stored persistence map from the storage device 324 to determine theactual resources allocated to the client station 300.

If the UL-MAP or DL-MAP explicitly allocates resources to the clientstation 300, the resource mapper 330 determines the resources directlyfrom the resource allocation. If neither UL-MAP nor the DL-MAPidentifies the client station 300, but instead relies on an earliercommunicated persistent allocation, the resource mapper 330 compares thepersistent allocations against the stored version to determine if anyallocation has been temporarily deactivated, and whether such temporarydeactivation affects the resources allocated to the client station 300.

The resource mapper 330 maps the uplink information to the properresources in a channelizer 350 based on the resource allocation. Forexample, the resource mapper 330 can be configured to control thesubcarriers and symbols that UL information is mapped to in thechannelizer 350.

The output from the channelizer 350, which can specify, for example, aseries of OFDM symbols, is coupled to the synchronizer 360 that can beconfigured to synchronize the symbol timing to the timing of the framesin which the uplink or downlink resource is allocated. The output of thesynchronizer 360 is coupled to a transmitter 370 that uses theinformation to create a signal that is upconverted to a desiredoperating frequency before it is transmitted using the antenna 302. Theoutput of the synchronizer 360 is also coupled to the receiver 310 tofacilitate receipt of the downlink allocation.

A NACK/ACK generator 332 can be coupled to the output of the DL/UL-mapmodule 320 and can be configured to generate an appropriate ACK or NACKmessage based on the ability of the DL/UL-map module 320 to recover anddecode the persistent resource allocation IE in the DL-MAP or theUL-MAP. The NACK/ACK generator 332 determines and couples theappropriate NACK or ACK message, if any, to the channelizer 350 fortransmission to the base station. The NACK/ACK generator 332 canselectively generate the NACK or ACK message to indicate the successfulreceipt of a persistent resource allocation IE, the presence or absenceof a persistent resource allocation IE error condition and the like.

One issue that is advantageously addressed with respect to persistentallocations is how to handle a map error. A map error occurs when aclient station fails to properly receive the persistent downlink oruplink map IE in a frame which may have included a change to itspersistent allocation. If a client station experiences a map error, itmust refrain from using the persistent allocation or risk transmittingon an allocation assigned to another client station, possibly corruptingboth transmissions. Similarly, if a client station experiences a maperror in a downlink resource allocation, the client station notifies thebase station. In order to avoid failed attempts to decode allocationsgranted to some other client station, the client station may refrainfrom attempting to decode data according to its most recent downlinkpersistent allocation until the error condition is corrected. On theother hand, according to one aspect, the client station may continue todecode data according to its most recent downlink persistent allocationuntil the map error condition is addressed, relying on the physicallayer (PHY) and media access (MAC) layer data error detection/correctionmechanisms commonly in use on wireless systems to correct any dataerrors that may occur if its most recent downlink persistent allocationis no longer valid. In this way, if the map error was associated with adownlink persistent allocation map in which no changes were made to theclient station's downlink persistent allocation, the data communicationcan continue without interruption. Obviously, it is advantageous for theclient station to resume the uplink communications on the properpersistent resource allocation or the downlink reception on the properresource allocation as soon as possible. Therefore, it is advantageousif the persistent allocation method employs an efficient error detectionand correction mechanism with very low latency between the occurrence ofa map error and the correction of the error condition.

According to the prior art, map errors may be addressed by having theclient station send an affirmative acknowledgment (ACK) to the basestation every time it properly receives a persistent downlink or uplinkmap IE which includes an update for the client station. Thus, eachclient station with a persistent allocation can also be assigned adedicated persistent ACK channel. One disadvantage of assigning eachclient station a dedicated persistent ACK channel is that there issignificant overhead associated with allocating and using thesededicated ACK channels. Even if allocation of the dedicated ACK channelis restricted to the client stations having higher probability ofexperiencing map error, such as client stations operating at the edge ofthe coverage area, the overhead associated with affirmativeacknowledgement is still significant. However, according to one aspectof the invention, such an embodiment can be implemented in conjunctionwith the shared NACK channel described more fully below such that clientstations more like to experience a MAP error are assigned eitherdedicated or sparsely shared NACK channel.

In another embodiment, map errors can be addressed by implementing NACKbased error recovery. If a client station experiences a map error, itsends a negative acknowledgment (NACK) message to the base stationindicating the map error. According to the prior art, the base stationcan allocate dedicated NACK channel associated with just one subscriberstation. However, using dedicated NACK channels can require asignificant amount of system resources as the number of client stationsusing the system gets large.

According to one aspect of the invention, a limited number of sharedNACK channels are used. Each shared NACK channel can be used by morethan one subscriber station to indicate a map error. The NACK messagecan include virtually any number of bits and information. However, inorder to reduce overhead, the NACK message can have as few as one bit,whose presence indicates the NACK. In other words, upon receipt of amessage on the shared NACK channel, the base station determines that oneor more of the client stations associated with the NACK channel hasexperienced a map error. However if multiple client stations are usingthe NACK channel, the base station cannot specifically identify theclient station which experienced the map error.

The base station can specify the modulation coding scheme assigned tothe NACK channels, for example, in the persistent resource allocationIE. However, due to the potentially low bandwidth of the information onthe NACK channel, and a desire to successfully report NACK in case ofmap error, the modulation coding scheme associated with the NACKchannels can be fixed to a robust modulation coding scheme and a highlyrepetitious coding. In one embodiment, the modulation coding schemeassociated with the NACK channels is BPSK. In another embodiment, themodulation coding scheme associated with the NACK channels is QPSK withrate 1/2 coding according to a predetermined encoding scheme. Of course,the modulation coding schemes can be virtually any type of fixed ordynamically specified schemes.

According to IEEE 802.16, the client stations use pseudorandom codes todefine the MAP NACK channel. In one embodiment, one common pseudorandomcode can be assigned to, or otherwise used by, more than one clientstation to indicate a map error. In such a case, the base station doesnot know which or how many client stations experienced a map error uponreceipt of an error indication on the NACK channel. However, accordingto one aspect, the base station can determine the group to which theclient station is assigned based on the frame in which the map NACKchannel message is received and, in some cases, the particularpseudorandom code if more than one is used. When using pseudorandomcodes, if more than one client station sends a map NACK channel message,the energy from each client station can be combined in a macro-diversitysense, according to the standard operation of the physical layer, thusenhancing the probability of reception.

FIGS. 4 through 8 detail an embodiment of error correction in persistentuplink resource allocation utilizing NACK messaging. The embodiments anddescription are focused on correcting persistent downlink or uplink maperrors in a time division multiplex (TDM) OFDMA system. However, theapparatus and methods for error correction in persistent resourceallocations are not limited to pseudorandom NACK messaging nor are theylimited to TDM or OFDMA systems.

NACK Messaging for Persistent Error Correction

FIG. 4 is a simplified timing diagram 400 of an embodiment of apersistent resource allocation. The persistent resource allocationembodiment illustrated in the timing diagram of FIG. 4 supports TimeDivision Duplex (TDD) operation of downlink and uplink subframes, andmultiple persistent resource groups within a persistence period.Additionally, the timing diagram is described in the context ofpersistent uplink resource allocation with a K+1 allocation relevance(resources allocated in the resource allocation IE message of frame Kare active in frame K+1) and persistent downlink resource allocationwith a relevance of K. However, the error correction for persistentresource allocation methods and apparatus described herein are notlimited to TDD operation, multiple resource groups, or any particularresource allocation relevance. This error recovery mechanism describedherein allows for fast error detection for both DL and UL persistentallocations.

The timing diagram 400 of FIG. 4 illustrates a number of successiveframes 420, e.g. 420-K through 420-(K+8), where each frame includes adownlink subframe 412 followed by an uplink subframe 414. The frames arefurther divided into persistence groups 410, such as persistent groups410-N and 410-(N+1), with each persistence group 410 including a fixednumber of frames 420. The period of one persistence group is referred toas an allocation period (AP) or persistent period.

Each frame 420 in a persistence group 410 can be associated with apersistence index, also referred to as a group cycle index, which can beused to identify the position of the frame within the persistence group410. As described previously, a persistent downlink or uplink resourceallocation may be associated with a particular group cycle index. InFIG. 4, the allocation period is four frames. Thus a persistent uplinkresource allocated to the Kth UL subframe 414-K applies to the ULsubframe in the frame 420-(K+4) of the next persistence group 410-(N+1).Similarly, a persistent downlink resource allocated to the Kth downlinksubframe 412-K applies to the downlink subframe in which it occurs (i.e.DL subframe 412-K.) In both the downlink and uplink, persistenceresource allocations remain valid for successive frames.

A persistent resource allocation IE 430-K can specify an uplink ordownlink persistent resource allocation or both. In one aspect an uplinkpersistent resource allocation received in a downlink subframe 412-K canhave a relevance of K+1, such that the uplink resources allocated in theKth DL subframe 412-K occur in the K+1 uplink subframe. The persistentresource allocation IE 430-K received in a downlink subframe 412-K canhave a relevance of K for downlink allocations, such that the downlinkpersistent resources 434 allocated in the Kth DL subframe 412-K occur inthe Kth downlink subframe.

With a four frame persistent allocation (the typical case for VoIP), itis advantageous to design a system to recover from a map error beforethe next scheduled persistent allocation. Thus the impact of map erroron quality of service (QoS) is substantially the same as for persistentand non-persistent allocations.

The persistence allocation IE 430-K typically allocates the resourcesusing multiple pieces of information. The information in the persistenceallocation IE 430-K can include a CID or reduced connection identifier(RCID)—indicating the connection for which this persistent allocation isdirected. (A RCID is an abbreviated connection identifier which containsfewer bits than the CID but still completely identifies the connection.)The information can also include an indication of the allocation period,illustrated above as the period of the persistence group 410. If aclient station is allocated a persistent allocation in frame K using thepersistent IE, the client station also has an allocation in framesK+N*AP, where N represents the number of persistence groups and AP isthe allocation period measured in units of frames. A typical IEEE 802.16allocation period is 20 ms, corresponding to four 5 ms frames,representing the packet emission rate of most commonly used codecs.

The information in the persistence allocation IE 430-K can also includean allocation unit offset, which may also be referred to as a slotoffset. The slot offset is used to indicate the start of the persistentallocation relative to a known starting point. For example, in HARQallocation, the slot offset is relative to the beginning of the HARQregion. As another example, in UL non-HARQ allocation, the offset isrelative to the start of the UL sub-frame. The information can alsoinclude a number of slots, also referred to as a duration. The durationindicates the number of consecutive slots in the persistent allocation.

The information can also include PHY related information (e.g.modulation and coding, etc.) In addition the information can include anHARQ ACK channel index (in the case of HARQ allocation) that indicates aspecific HARQ ACK channel to use to acknowledge receipt of HARQ packetsover the persistent resource allocation. The HARQ ACK channel is alsoallocated persistently with the same period as the data resourceassignment so that each HARQ packet received can be properlyacknowledged.

In one embodiment, a dedicated map ACK channel can be defined for eachsubscriber station. The subscriber station sends a map ACK each time itsuccessfully receives a downlink or uplink map IE. However, thisapproach requires the establishment of a great number of map ACKchannels as well as the transmission of many responsive acknowledgments.

To facilitate addressing map errors in a more efficient manner, theinformation in the persistence allocation IE 430-K can also include amap NACK channel index. The map NACK channel index identifies a specificmap NACK channel used by the client station to indicate that it was notable to decode a persistent map IE. As described above, the NACK channelmay be assigned to the individual client station or it may be sharedamong multiple client stations.

FIG. 5 is a simplified timing diagram 500 of an embodiment of map NACKmessaging in a system having persistent resource allocation and multiplemap NACK channels.

UL sub-frame 414 K+1 contains the map NACK channels 510-(K+1), 512-(K+1)and 514-(K+1) for Frame K 420-K. The timing diagram 500 illustratesthree map NACK channel subgroups, indexed a 510-(K+1), b 512-(K+1), andc 514-(K+1). Client stations are assigned to one of these map NACKsub-groups: a, b or c. This allows the base station to narrow the groupof possibly affected client stations when a map NACK message isreceived.

In an embodiment, the base station allocates one or more fast feedbackslots for the purpose of creating one or more map NACK channels. In oneaspect, the map NACK Channel (MNCH) can be allocated a pseudorandom codeto indicate a map error condition, with different codes assigned to thevarious subgroups.

The base station receives a NACK message from one or more clientstations that did not properly decode a persistent downlink or uplinkmap IE which may carry information for that client station. In otherwords the base station receives a NACK message from any users whoexperienced a map error.

In another embodiment, which can be used with or without the subgroupsdescribed above, if the base station receives a map NACK channel messageand no changes were made to the persistent allocations in thecorresponding frame, the base station sends a short message indicatingthat there were no changes. In this way the base station avoidsresending a full or partial persistent downlink or uplink mapinformation element in favor of a shorter “no changes” message.

Instead of or in conjunction with an express NACK, in one embodiment,rather than use the map NACK channel, the base station can use implicitmeans to detect map errors. When the client station experiences anuplink map error, it does not transmit in the next frame. Therefore, ifthe base station detects little or no signal energy was received from aclient station over the uplink during its uplink persistent allocationfor one or more frames, the base station can infer that the clientstation experienced a map error. This implicit method of map errordetection can be used alone or in conjunction with a map NACK channel orother error detection mechanisms. This implicit error detectionmechanism can be used to recover from a map NACK channel error asdiscussed below.

As described above, or in one aspect the map NACK channel is specifiedwithin the persistent downlink or uplink map information element. Aproblem may occur if a client station experiences a map error in apersistent allocation information element in which it is eitherinitially assigned a map NACK channel or its map NACK channel ischanged. In the first case, the client station does not know what mapNACK channel to use. In the second case, the client station uses a mapNACK channel that the base station does not associate with this clientstation. In a third case, the client station properly uses a currentlyassigned map NACK channel but the message is not properly received bythe base station. We refer to this problem as a map NACK channel erroror map NACK channel assignment error.

There are several embodiments which can address a map NACK channelerror. In one embodiment, the base station uses implicit means to detectmap NACK error. For example, if the base station detects little or nosignal energy was received from a client station during one or more itsuplink persistent allocations, the base station can infer that theclient station experienced a map error and a map NACK channel error andcan resend the persistent allocation information, including the map NACKchannel assignment.

In the case in which the map NACK message is properly sent but is notproperly received by the base station, in one embodiment, a map NACKchannel error can be detected by the client station. If a client stationsends a message on the map NACK channel and does not get the expectedresponse from the base station in the next persistent map IE ofinterest, the client station assumes that the base station did notreceive the map NACK channel message. Therefore, according to thisaspect, the client station sends another map NACK message. In this case,when a base station receives a map NACK message it does not know whetherthe NACK message was a first or a second transmission. If this scheme isused, it may be advantageous for the base station to send updatesassociated with one or more frames worth of updates. For example, inresponse to each successfully received message on the map NACK channel,the base station can repeat all changes affected within the last tworelevant frames.

FIG. 6 is a simplified flowchart of an embodiment of a method 600 ofpersistent downlink or uplink resource allocation. The method 600 can beimplemented, for example, within a base station of FIG. 1 or FIG. 2 toenable NACK messaging used to perform error correction in persistentresource allocations. The persistent resource allocation can be aninitial persistent resource allocation or can be an updated persistentresource allocation.

The method 600 begins at block 610 where the base station determinesthat a particular client station, or communication link established withthe client station, is a candidate for persistent resource allocation.The base station proceeds to block 620 and schedules the client stationfor persistent resource allocation. The persistent resource allocationis valid for more than one frame. The persistent resource allocation canbe specified according to a number of time division multiplexedpersistence resource groups. Each group may be associated with apersistence slot index that identifies a downlink or uplink frame ineach resource allocation period. The base station can assign the clientstation to one of the persistence groups, for example, to balance thepersistent resource loading across the allocation period.

The base station proceeds to block 630 and assigns the client station toa NACK subgroup within its persistence group. Each NACK subgroup can beassociated with a distinct map NACK channel assignment. The base stationcan utilize NACK subgroups with a plurality of client stations assignedto subgroups in order to reduce the resources needed to support NACKchannels. A NACK message received by the base station on a map NACKchannel associated with a particular subgroup affects all clientstations associated with the group and NACK subgroup. The base stationcan base the retransmission on the identified client stations. The basestation can operate to substantially uniformly distribute clientstations across the various subgroups.

The base station proceeds to block 640 and generates for the clientstation a persistent resource allocation IE with a map NACK channelassignment. The base station proceeds to block 650 and transmits thepersistent resource allocation IE with a map NACK channel assignment,for example, as part of a DL-MAP or UL-MAP message. The base stationproceeds to block 660 and is done with the current persistent resourceallocation for a client station.

FIG. 7 is a simplified flowchart of an embodiment of a method 700 ofresource reallocation in the presence of error correction. The method700 of FIG. 7 can be implemented, for example, within a base station ofFIG. 1 or FIG. 2.

The method 700 begins at block 710 where the base station sends apersistent allocation IE with a NACK channel assignment to one or moreclient stations in its serving area. The base station can, for example,generate and send the message using the method of FIG. 6.

The base station proceeds to decision block 720 and monitors thereceived uplink signals to determine whether a NACK message is receivedduring an assigned NACK channel. A presence of a NACK message is anexpress indication of a map error condition, while absence of a NACKmessage does not ensure the absence of a map error condition.

If the base station determines, at decision block 720, that an expressNACK message is received, the base station proceeds to block 740.Alternatively, if the base station determines, at decision block 730that no NACK message has been received, the base station proceeds todecision block 730.

At decision block 730, the base station determine the presence of a maperror condition implicitly. That is, the base station, based on one ormore parameters implicitly determines the presence of a NACK. Forexample, the base station may monitor uplink resource allocations andmay imply a NACK for any uplink resource allocation for which notransmission is received. If the base station determines that noimplicit NACK is present, the base station determines an absence of amap error condition and returns to block 710. Alternatively, if the basestation, at decision block 730, implicitly determines the presence of aNACK, the base station proceeds to block 740.

At block 740, the base station identifies the client station or group ofclient stations associated with a NACK message or indication. Forexample, the base station can examine the NACK channel, persistencegroup, and subgroup associated with a NACK message to identify one ormore client stations. Alternatively, the base station can correlate amissing uplink transmission with a client station allocated the uplinkresources to determine an identity of a client station.

After determining the identity of one or more client stations associatedwith a NACK message or indication, the base station proceeds to block750 and determines the portion of a previously transmitted uplinkresource allocation IE relevant to the identified client stations. Thebase station can format an updated persistent resource allocation IErepeating a portion of a previously transmitted uplink resourceallocation IE relevant to the identified client stations. Alternatively,if no portion of a previously transmitted uplink resource allocation IEis relevant to the identified client stations, the base station cantransmit a “no change” persistent resource allocation IE message. Thebase station returns to decision block 720 to determine if the latestresource allocation IE message is a source of map errors.

FIG. 8 is a simplified flowchart of an embodiment of a method 800 oferror correction signaling in a client station. The method 800 can beimplemented, for example, in a client station of FIG. 1 or FIG. 3.

The method 800 begins at block 810 where the client station receives aDL-MAP or an UL-MAP having a persistent resource allocation IE message.The client station proceeds to decision block 820 to determine if it isable to successfully decode the map and, in particular, the persistentresource allocation IE message. If so, the client station proceeds toblock 840 to process the map for any resource allocations to the clientdevice. The client device proceeds to block 850. Alternatively, if theclient station is unable to successfully decode the map message, theclient station proceeds from decision block 820 to decision block 830.

At decision block 830, the client device determines if it is already arecipient of a persistent resource allocation, such as a persistentuplink resource allocation or a persistent downlink resource allocation.If, at decision block 830, the client station determines that it has noactive persistent resource allocation, the client station proceeds toblock 832 in which it optionally generates ands send a global NACK toindicate the failure to potentially receive the initial resourceallocation. The client station returns from block 832 to block 810 toawait the next DL/UL map transmission, which likely includes aretransmission of any missed persistent resource allocation.

If, at decision block 830, the client station determines that it haspreviously been allocated persistent resources, the client stationproceeds to block 834 to temporarily deallocate the client station fromthe prior persistent resource allocation to prevent potential corruptionof another device's transmissions.

The client device proceeds from block 834 to block 860 and determinesits associated map NACK channel assignment. The client station proceedsto block 870 and transmits the NACK on the assigned map NACK channel.The client station returns to block 810 to await the transmission of asubsequence persistent UL allocation IE.

FIG. 9 is a more detailed flowchart of an embodiment of a method 900 ofaddressing a persistent allocation map error from the perspective of abase station. The method 900 can be implemented, for example, within abase stations such as the one shown in FIG. 1 or FIG. 2.

The method 900 begins in block 910 in which the base station determineswhether a map NACK message was received in frame K. For example, thebase station 200 may determine whether a map NACK message was receivedover a shared map NACK channel. In one embodiment the map NACK channelis received over the receiver 210 (FIG. 2) over a shared random accesschannel. In such an embodiment, the map NACK message may comprise apseudorandom sequence the presence of which specifies a map NACK erroris being indicated by a client station assigned to the shared map NACKchannel. Referring again to FIG. 2, the random access channel processor220 determines whether a map NACK message was received.

If no map NACK was received in frame K, flow continues to block 912 inwhich the frame counter is incremented. Flow continues back to block 910for analysis of the next frame.

If a map NACK was received in frame K, flow continues from block 910 toblock 914. In block 914, the base station determines whether it has areason to send all persistent allocation assignments. For example,within the base station 200, the persistent DL/UL IE gyrator 250determines whether it intends to send all currently active persistentallocation assignments.

If the base station 200 determines that it will send all currentlyactive persistent allocation assignments, flow continues to block 916.In block 916, the base station creates a persistent DL_map IE indicatingall persistent allocations. For example, the persistent DL/UL IEgenerator 250 creates such a message and provides the information to theDL map generator 260 for combination with other allocations. The DL mapgenerator 260 provides the map information to the downlink processor 270which formats the message for proper transmission over the wireless linkvia the transmitter 280 and an antenna 202 (such actions being omittedfrom FIG. 9 for clarity.)

If the base station determines that it need not send all currentlyactive persistent allocation assignments, flow continues from block 914to block 918. In block 918 the base station determines whether changesto the persistent allocations were made in recent downlink map IE's. Forexample, if the system is configured such that a client station may sendone additional map NACK messages if it does not receive an expectedresponse to a first map NACK message, the persistent DL/UL IE generatordetermines whether any changes to the persistent allocations were madein the two previous relevant frames. If changes were made, flowcontinues to block 920 in which the base station creates a DL_map IEindicating the receipt of a map NACK and repeating any persistentallocation changes that were made in the relevant frames. For example,referring again to FIG. 2, the persistent DL/UL IE generator 250 createsa message indicating receipt of a map NACK message and repeating therelevant persistent allocation changes. This information is sent overthe wireless link in the manner just described.

If the base station determines that no changes were made in block 918,flow continues to block 922 to. In block 922, the base station creates apersistent downlink map IE indicating receipt of the map NACK and thatno changes have been made. For example, the persistent DL UL IEgenerator 250 creates such a “no-changes” message and this informationis sent over the wireless link in the manner just described.

FIG. 10 is a more detailed flowchart of an embodiment of a method 1000of addressing a downlink persistent allocation map error from theperspective of a client station. The method 1000 can be implemented, forexample, within a client station such as the one shown in FIG. 1 or FIG.3. Although FIG. 10 is described in the context of a downlink map error,a similar process can be used to address an uplink map error.

In block 1002, the client station determines whether it is expecting apersistent DL_map in frame K. If not, flow continues to block 1004 inwhich the frame count is incremented. If the client station is expectinga persistent DL_map, flow continues to block 1006. In block 1006, theclient station determines whether the expected downlink persistentallocation map was properly received. For example, downlink messagingfrom the base station is received over the downlink 116 a via theantenna 302 and the receiver 310 of the client station 300, as shown inFIG. 3. The DL/UL map module 320 determines whether the downlink map wasproperly received. If the downlink map was properly received, flowcontinues to block 1004 in which the frame counter is incremented.

If the downlink map was not properly received, a map error has occurredand flow continues to block 1008. In block 1008, the client stationinterrupts transmissions on any uplink control messaging associated withany active downlink persistent allocation, such as an HARQ ACK channelassociated with the downlink persistent allocation. In one embodiment,the client station also stops attempting to decode downlink messagingaccording to any active persistent allocation in order to avoid failedattempts to decode downlink allocations granted to some other clientstation. On the other hand, according to one aspect, the client stationmay continue to decode data according to any active downlink persistentallocation until the map error condition is addressed, relying on thephysical (PHY) layer and media access (MAC) layer data errordetection/correction mechanisms commonly in use on wireless systems tocorrect any data errors that may occur if its most recent downlinkpersistent allocation is no longer valid. In this way, if the map errorwas associated with a downlink persistent allocation map in which nochanges were made to the client station's downlink persistentallocation, the data communication can continue without interruption.

Although it typically happens infrequently, the base station may re-mapthe resource associated with a shared NACK channel. For example, thebase station may assign a new pseudorandom code to a shared NACKchannel. Such a change is typically reported to the client station in anUL-MAP information element. If a client station fails to receive anUL-MAP information element which defined a new shared NACK channel, itmay send a NACK message over an incorrect channel. Thus, according toone aspect of the invention not shown in FIG. 10, the client stationdetermines whether the uplink map is properly received in the relevantframe following a failure to properly receive a downlink map. Forexample in FIG. 3, the DL/UL map module 320 determines whether theuplink map in relevant frame was properly received. If not, the clientstation cannot be sure that its NACK channel information is current anda map NACK channel error recovery procedure may begin without the clientstation sending a message on the shared NACK channel.

Flow proceeds to block 1014 in which the client station sends a downlinkmap NACK message in the proper frame. In one aspect, such as the oneshown in FIG. 10, the delay between the occurrence of a map error andthe transmission of the NACK is a predetermined value so that the basestation can determine the affected persistence group based on the framein which the map NACK is received. In FIG. 10, for purposes of example,the map NACK is sent two frames after the occurrence of the map error.

In one aspect, the client station sends a pseudorandom code over ashared DL map NACK channel in which the presence pseudorandom codeindicates to the base station that one or more of a set of clientstations using the shared DL map NACK channel has experienced an error.The DL/UL map module 320 passes is information to the NACK/ACK module332 the NACK/ACK module 332 creates the shared channel pseudorandomcode. The channelizer 358 receives the message which is transmitted overthe uplink 116 via the synchronizer 360, the transmitter 370 and theantenna 302.

In block 1015, the frame count is incremented and the client stationawaits the arrival of the next frame in which it expects to receive apersistent allocation map.

In block 1016, the client station determines whether it has received aDL map IE in a subsequent frame including a persistent downlinkallocation expressly addressed to the client station. If so, in block1018, the client station uses the newly assigned persistent allocation.Flow continues through block 1004.

If the client station does not receive a persistent downlink mapinformation element including a persistent downlink allocation expresslyaddressed thereto in block 1016, flow continues to block 1022. In block1022, the client station determines whether it has received a persistentdownlink map IE indicating that a NACK message was received but that nodownlink map changes were made within the relevant frames. If so, flowcontinues to block 1020 and the client station resumes use of anypersistent allocations which were active at the time of the map error.

In the embodiment shown in FIG. 10, if the client station does notreceive a downlink map as expected, a map NACK channel error hasoccurred and the map NACK channel error recovery process begins in block1030. In one aspect, the map NACK error recovery process does notcommence until the client station has sent more than one map NACK, inwhich case, after the first pass through block 1024, the frame counterwould increment and flow could continue back to block 1014.

The process for addressing a persistent map error for the uplink map issimilar to the one shown in FIG. 9 for the base station and in FIG. 10for the client station. In block 1008, it would be prudent to refrainfrom using any active uplink, persistent allocation to avoid the risk oftransmitting on an allocation which was assigned to another clientstation in the missed map, possibly corrupting both transmissions.

As described above, a map NACK channel error can occur if the basestation fails to receive the map NACK message. In block 1030 of FIG. 10the client station begins a map NACK channel error recovery process dueto a map NACK channel error. In one aspect, the client station sends amap NACK channel error indication on a dedicated channel, such as byusing an express MAC layer message.

In another aspect, the base station uses MAC layer information toimplicitly determine a map NACK channel error and the client stationneed not expressly address a map NACK channel error. If the channel isestablished using a Hybrid Automatic Repeat-reQuest (HARQ) error controlmethod, each time the base station sends a downlink data packet to theclient station it expects to receive from the client station over theuplink either an acknowledgment (ACK) indicating that the packet wassuccessfully received or a negative acknowledgment (NACK) indicatingthat the packet was not successfully received, according to well knownprinciples. If the base station fails to receive either a packet ACK orpacket NACK for one or more HARQ packets, the base station can inferthat a map NACK channel error has occurred. Likewise, if the basestation fails to generate either a packet ACK or a packet NACK for oneor more uplink HARQ packets, the base station can infer that a map NACKerror has occurred. In one aspect, the base station responds to theabsence of an HARQ ACK and NACK in the same manner as it was if itreceived a message over the NACK channel, such as in step 910 of FIG. 9.In this case, the base station knows the identity of the client stationand can address the error specifically without regard to the otherclient stations in the persistence group.

A map NACK channel error can occur when a client station which is notcurrently assigned a persistent downlink or uplink allocation does notproperly decode the persistent map IE which assigns to it a persistentallocation. This scenario is referred to as a lost invitation error. Inthis case, the client station may not been assigned a map NACK channelover which to send an indication of the map error. In one embodiment,the HARQ error detection method just described is used only the firsttime a persistent allocation is made in order to address a lostinvitation error. After the initial persistent allocation is made and aseries of packet ACKs and packets NACKs are received, the base stationcan assume that the client station as properly decoded the persistentmap information element and has the information it needs to use the mapNACK channel.

According to another aspect, the base station defines a global map NACKchannel in addition to the persistent group map NACK channels discussedabove. The global map NACK channel is used to address lost invitationerrors. The base station advertises the global map NACK channelinformation in the Uplink Channel Descriptor (UCD) rather than in thepersistent uplink map IE so that all client stations in the system areaware of the global map NACK channel, whether or not they are currentlyassigned an active persistent allocation. This global map NACK channelis used only by users without a persistent resource allocation if theyfail to receive a persistent map IE. For example, if the client stationhad no active persistent allocation at the time the map error wasdetected in block 1006, the client station sends a NACK message over theglobal map NACK channel rather than a map NACK channel shared by apersistence group or subgroup as shown in block 1014. Alternatively orin addition, a client station which has detected a map NACK channelerror can send a NACK message on the global map NACK channel as part ofthe recovery process. For example, in response to a lost invitationerror, a client station which executed the process shown in FIG. 10 maysend a global map NACK message as part of the map NACK channel errorrecovery process of block 1030.

When using a global map NACK channel, the base station implements acorresponding process similar to one shown in FIG. 9 with respect to theglobal map NACK channel. In response to receipt of a message over theglobal map NACK channel (similar to block 910), in a similar manner toblock 914 the base station determines whether it had a reason toretransmits all persistent allocations. The base station determines: anynew persistent allocations were made (similar to block 918.) If no newpersistent allocations were made in the frame of interest, the basestation can either send a no-changes message (similar to block 922) orsimply ignore the global map NACK message. If new persistent allocationswere made in the frame of interest, the base station can repeat eitherthe entire persistent downlink and/or uplink map IE or send a partialpersistent map IE including all the newly initiated persistentallocations (similar to blocks 916 and 920.) Users with persistentresource allocations typically use the map NACK channel index indicatedin the persistent allocation IE rather than a global map NACK channel.The global map NACK channel can be used in conjunction with one or moreerror recovery techniques.

In yet another embodiment, the base station defines one or moreuniversal map NACK channels. The universal map NACK channel is used toaddress lost invitation errors. For example, the base station advertisesone or more universal map NACK channels in the UCD. In addition, beforethe first persistent allocation is made for a client station, the basestation sends a group cycle index to the client station over an assureddelivery service. The assured delivery service ensures that a message isreceived by the client station. For example such a link requires anacknowledgment from the client station before the message is consideredto have been successfully transmitted. In an 802.16 system, the basestation may use a delivery assured dynamic service (DSx) message to sendthe group cycle index to the client station. Client station may use theuniversal map NACK channels only after it has been allocated a map NACKindex. In this way, client stations which are neither using nor acandidate to use a persistent allocation do not send messages over theuniversal map NACK channel thus reducing overhead. Once the base stationreceives a message on the universal map NACK channel, if no newpersistent allocations were made in the frame of interest, the basestation can either send a “no changes” message or simply ignore theuniversal map NACK message. If new persistent allocations were made inthe frame of interest, the base station can repeat either the entirepersistent uplink map IE or just send a partial persistent downlink oruplink map IE. In one embodiment, the universal map NACK channel is usedin addition to the map NACK channel specified in the persistent downlinkor uplink map IE as discussed above.

In yet another embodiment, lost invitation errors are addressed using atemporary map ACK channel. Whenever a new persistent allocation is made,the persistent map IE includes a map ACK channel for use by the clientstation only to acknowledge this first allocation. If the base stationfails to receive a message on the map ACK channel, the base station actsin the same manner as if it received a message over the map NACKchannel. Once the client station has successfully received thepersistent map IE, it indicates subsequent map errors in loss using themap NACK channel assigned using the persistent allocation IE.

As used herein, the term coupled or connected is used to mean anindirect coupling as well as a direct coupling or connection. Where twoor more blocks, modules, devices, or apparatus are coupled, there may beone or more intervening blocks between the two coupled blocks.

The steps of a method, process, or algorithm described in connectionwith the embodiments disclosed herein may be embodied directly inhardware, in a software module executed by a processor, or in acombination of the two. When implemented in software, firmware,middleware or microcode, the program code or code segments to performthe necessary tasks may be stored in a machine readable medium such as astorage medium. The various steps or acts in a method or process may beperformed in the order shown, or may be performed in another order.Additionally, one or more process or method steps may be omitted or oneor more process or method steps may be added to the methods andprocesses. An additional step, block, or action may be added in thebeginning, end, or intervening existing elements of the methods andprocesses

The above description of the disclosed embodiments is provided to enableany person of ordinary skill in the art to make or use the disclosure.Various modifications to these embodiments will be readily apparent tothose of ordinary skill in the art, and the generic principles definedherein may be applied to other embodiments without departing from thescope of the disclosure.

What is claimed is:
 1. A method of performed by a client station, themethod comprising: receiving, by the client station, persistent resourceallocation information, the persistent resource allocation informationincluding an indication of downlink (DL) persistent resources, a firstidentifier associated with the client station, an indication of a DLallocation period, an indication of uplink (UL) persistent resources,and an indication of an UL allocation period; periodically receiving, bythe client station, DL user data associated with the first identifier,the DL user data being received via the DL persistent resources andbased on the DL allocation period, and the DL persistent resourcesrepeating at an interval defined by the DL allocation period; andpersistently transmitting, by the client station, UL user data via theUL persistent resources and based on the UL allocation period, the ULpersistent resources repeating at an interval defined by the ULallocation period.
 2. The method of claim 1, further comprising:receiving non-persistent resource allocation information including anindication of non-persistent resources and a second identifierassociated with the client station; and receiving second DL user dataassociated with the second identifier using the non-persistentresources.
 3. The method of claim 1, further comprising: subsequent toreceiving the persistent resource allocation information, receiving anindication of a release of the persistent resources; and transmitting anindication of a positive acknowledgement (ACK) of the release.
 4. Themethod of claim 1, wherein the DL allocation period is different thanthe UL allocation period.
 5. The method of claim 1, further comprising:receiving an offset indication, wherein the offset indication indicatesan offset in a region of the UL persistent resources, wherein the ULpersistent resources are based; and the persistently transmittingfurther including transmitting the UL user data via resources based onthe offset.
 6. The method of claim 1, wherein the persistent resourceallocation information is received via a control channel, and whereinthe DL user data is received via a shared channel.
 7. The method ofclaim 1, wherein at least one of the UL persistent resources and the DLpersistent resources are used in voice over Internet protocol (VoIP)communication.
 8. The method of claim 1, wherein the persistent resourceallocation information further includes an indication of UL resourcesfor hybrid automatic repeat request (HARQ) information.
 9. The method ofclaim 1, wherein the receiving the persistent resource allocationinformation includes receiving a plurality of persistent resourceallocation messages.
 10. The method of claim 1, wherein the firstidentifier is selected from a predetermined range of values.
 11. Aclient station comprising: a receiver operable to: receive persistentresource allocation information, the persistent resource allocationinformation including an indication of downlink (DL) persistentresources, a first identifier associated with the client station, anindication of DL allocation period, an indication of uplink (UL)persistent resources, and an indication of an UL allocation period; andperiodically receive DL user data associated with the first identifier,the DL user data being received via the DL persistent resources andbased on the DL allocation period, and the DL persistent resourcesrepeating at an interval defined by the DL allocation period; and atransmitter operable to persistently transmit UL user data via the ULpersistent resources and based on the UL allocation period, the ULpersistent resources repeating at an interval defined by the ULallocation period.
 12. The client station of claim 11, wherein thereceiver is further operable to: receive non-persistent resourceallocation information including an indication of non-persistentresources and a second identifier associated with the client station;and receive second DL user data associated with the second identifierusing the non-persistent resources.
 13. The client station of claim 11,wherein: the receiver is further operable to, subsequent to receivingthe persistent resource allocation information, receive an indication ofa release of the persistent resources; and the transmitter is furtheroperable to transmit an indication of a positive acknowledgement (ACK)of the release.
 14. The client station of claim 11, wherein the DLallocation period is different than the UL allocation period.
 15. Theclient station of claim 11, wherein: the receiver is further operable toreceive an offset indication, wherein the offset indication indicates anoffset in a region of the UL persistent resources; and the transmitteris further operable to transmit the UL user data via resources that arebased on the offset.
 16. The client station of claim 11, wherein thepersistent resource allocation information is received via a controlchannel, and wherein the DL user data is received via a shared channel.17. The client station of claim 11, wherein at least one of the ULpersistent resources and the DL persistent resources are used in voiceover Internet protocol (VoIP) communication.
 18. The client station ofclaim 11, wherein the persistent resource allocation information furtherincludes an indication of UL resources for hybrid automatic repeatrequest (HARQ) information.
 19. The client station of claim 11, whereinthe persistent resource allocation information includes a plurality ofpersistent resource allocation messages.
 20. The client station of claim11, wherein the first identifier is selected from a predetermined rangeof values.